Safety control for machines



March 20, 1951 N. A. l.. GUILL ET AL 2,545,549

SAFETY CONTROL FOR MACHINES Filed DeC. 8, 1948 68 24 F/Gf l A) 25d 44 L l 58 54 25H 77 f5 Q o o- 55^| 69 au 5. M MA L Mam@ TTOR/VFV Patented Mar. 20, 1951 SAFETY CONTROL FoR MACHINES Nat A. L. Guill, Broadview, and Bror V.- Malmberg, Chcago, Ill., assignors to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application December 8, 1948, Serial No. 64,114

1 claim. 1

This invention relates to safety controls for machines, and more particularly to an electric two-hand safety control arrangement for material working machines.

An object of this invention is to provide a simple and efficient electric two-hand safety control arrangement for a material working machine which requires both hands of an operator to initiate a single cycle of operation of the machine and whereby a repeat operation of the machine cannot be effected until the operators hands are removed from the control arrangement and again applied thereto.

In accordance with the above object, the invention contemplates, in one embodiment thereof, as applied to controlling the operation of a conventional type punch press including a wellknown type of one-revolution clutch, an electric two-hand clutch trip safety control arrangement.

Specifically, the control arrangement comprises an air cylinder for actuating the clutch trip, the air under pressure to such cylinder being controlled by a solenoid controlled air valve operated through a circuit which includes a pair of double manually actuated push buttons normally in their out positions to allow current to energize an electromagnet for holding a mechanical latch out of holding engagement with a relay contact lever. Upon manual actuation ofA both push buttons by the use of both hands of the operator, the electromagnet is deenergized, effecting release of the latch and simultaneously therewith the relay is energized to pull its contact lever into position to close a circuit to a time delay relay, either electronic or of a synchronous motor type, which closes a circuit to energize and cause a normally open relay to close the solenoid controlled air Valve circuit for a predetermined time interval, whereupon the air valve is opened to permit air under pressure to flow into the air cylinder to actuate the clutch trip and thus initiate a single cycle of operation of the punch press. The arrangement is such that a repeat operating cycle of the punch press cannot be effected until the push buttons are manually released to permit their return to their normal out positions and again manually actuated.

Other objects and advantages of this invention will more fully appear from the following detailed description taken in conjunction with the accompanying drawing, in which Fig. l is a side elevational view of a material working machine having an electric two-handl safety control arrangement embodying the features of the invention applied thereto; and` Fig- 2 is a diagrammatic view illustrating an electric circuit for controlling the actuation of the air valve and cylinder for actuating the clutch trip of the material working machine.

(Cl. F- 335) ll?.eierring now to the drawing, it will be noted that the material workingv machine selected to illustrate the invention is a punch press, indicated generally at i0, and including the conventional driving means (not shown) for rotating the usual crank drive shaft upon which a flywheel ll4V is mounted. The conventional clutch mechanism is indicated in outline at i2 and is of the one-revolution type, normally in its inoperative position, with the ywheel unclutched from the crank driveV shaft. An operation of the clutch I2 is effected through the downward movement of a pull rod i3 operatively connected at its upper end in a suitable manner (not shown) to the trip operating portions of the clutch, its lower end being adjustably connected at i6 to a piston rod I9 of an air cylinder unit 20, the latter being supported by a bracket 24 mounted upon a base 25 of the press. The piston rod I9 and the connected pull rod I3 are normally urged upwardly through the force of a compression spring 25 to normally cause the clutch to be in its inoperative position.

It is not believed necessary to describe the structure of the press and its clutch in detail, it being understood that, upon tripping and operation of the one-revolution clutch I2, it will connect the driving means, including the flywheel ll andthe crank drive shaft, With a tool support 21 to move the latter, with a selected tool 28 mounted therein, through a complete cycle of operation from its upper position, through the material Working portion of its cycle and back to its normal or upper position. A die 30, carried by a die block 3l, mounted upon a bed plate 32, is positioned beneath the tool 28 to cooperate therewith when a material or article 33 is fed' to the die. The area, where work is performed uponk the material or article 33, through the'aid of the tool 28 and the die 3G, may be called the working position of the press. Into this position, it is generally necessary for one or both of the operators hands to move to position the material or article 33 and oftentimes to remove the worked material or article from the press. To assure that an operators hand or hands will not be positioned in this working area when the clutch I2 is tripped or set in operation is the purpose of the electric two-hand safety control arrangement of this invention, which will now be described.

Attached, as indicated in Fig. 1 at 34, to the bed' plate 32 of the press, one at each end thereof, are a pair of normally operable double push buttons or electric circuit controlling switches 36 and 31. The spaced switches 36 and 3i, as shown, face the front of the punch press where the operator is positioned, but it will be obvious that they may be mounted to Yface therefrom or parallel to the opposite end faces ofthe bed plate 3 32. The switches 35 and 3l are so positioned that the operator may conveniently reach and actuate them, but the safety control arrangement is such that the use or both hands is required to initiate each cycle of operation of the press. Also mounted upon the base of the press adjacent the air cylinder unit 2d, by means of a bracket 38, is a conventional type solenoid controlled spring returned air valve 39 for controlling the passage of air under pressure, supplied by an air supply line se to the valve from a suitable source, to the air cylinder unit by an air line 4I. An eX- haust air line for the cylinder unit 2li and air valve 3S is'indicated at 43 on the valve. When air is admitted to the cylinder unit 2li through the air valve 39, the piston rod i9 is moved downwardly and through the previously described connections the clutch l2 is tripped to initiate a single cycle of operation of the press. When the supply of air under pressure is cut off from the cylinder unit 29 by the air valve 39, the spring 25 acts to move the piston rod i9 upwardly and thus return the clutch tripping elements to their inoperative positions, which permits the clutch E2 to return to its normal inoperative position, thereby disengaging the iiywheel il from the crank drive shaft of the press. As the piston rod le of the cylinder unit 2i] moves upwardly and air 'through the valve 39 is cut ofi from the cylinder unit through the air line iii, the cylinder unit and air valve areexhausted through the air line 43.

In the operation of the electric two-hand safety control arrangement, the clutch l2 will be held inoperative to connect the flywheel Il, with the crank drive shaft of the press when the switches and si are permitted to move to their normal out positions, as shown inthe drawing, when the operator removes his hands therefrom, as will be apparent by consideration of the following description or the mode of operation of the control arrangement, taken in conjunction with Fig. 2, which is a diagrammatic view illustrating an electric circuit for controlling the actuation of the clutch i2. With the switches and 31 in their out positions, as just described, and assuming that a main switch as is closed, current will be supplied from one side of a lli) volt source lili through bridged stationary contacts 5G, 5i, 52 and of the switches 35 and 3l, through an electsomagnet of a suitable mechanical latching electrical reset relay 55 and back to the other side of the il@ volt source t5. The electromagnet 5d is thus energized and maintains a mechanical latch or" the relay 55Y out of engagement with a contact lever 59 of the relay 55.

To initiate a single cycle of operation of the punch press iii, the operator must push simultaneously on each of the switches 35 and 3l, using both hands, one on each of the switches, and in so doing, stationary contacts et, 6l, 62 and 63 of the switches are bridged, whereupon current will be supplied therethrough to the relay 55, which is energized and pulls its contact lever 59 into position with its contact El to close a circuit to an electronic timer et. Simultaneously with the energization of the relay 55, the circuit, through the electromagnet 5S, is broken, and it becomes deenergized and releases the latch 58, whereupon it moves into latching engagement with the contact lever 5S of the relay 55 under the urging of a connected tension spring 69.

The electronic timer 68, which may be any suitable timer, is capable, upon initiation of operalli tion, to immediately close a contact pair 10 and hold them closed for a predetermined interval of time and then open. Means included in the timer is provided for varying the timing interval. It is to be understood that the timer 68, after being set in operation in the manner described, will remain in operation for the predetermined set period of time and will not repeat until it receives a new impulse through a resetting of the mechanical latching relay 55. Upon closure of the contact pair lil, current will be supplied to a normally open relay ll, which is energized and pulls its contact lever 1li into position with its contact l5 to close a circuit to a solenoid 16, which has a movable core l1. The closure of the latter circuit moves the core i1 upwardly and since it is operatively connected to a movable spring returned element 'i8 of the valve 39, which controls the supply of air under pressure through the valve to the cylinder unit 20, the pull rod I3 is moved downwardly and the clutch I2 is thus tripped and a single cycle oi operation of the press is initiated. The energizing circuit to the solenoid le remains closed until the predetermined interval oi time controlled by the timer 68 runs out and such interval of time will agree with the time necessary to complete a single operation oi the press.

To cause the timer 68 to function again, whereby another cycle of operation of the press may be effected, the timer must receive a new impulse and this cannot be completed until the operator` releases both switches 35 and 3l, thereby causing the circuit to be closed again through the stationary contacts 5t, 5l, 52 and 53, thus energizing the electromagnet 54 which pulls back the latch 58 and releases contact lever 59 of the relay 55, which, at the same time, is deenergized, the contact lever opening the circuit to the timer 53 at its contact el, and conditioning itto again receive an impulse. The safety control arrangement has now been returned to its normal condition and another impulse to the timer 68 can now be made to cause another cycle of operation of the press by the operator again using both hands to push the switches 35 and 3'! to again bridge the stationary contacts 6U, 5I, 62 and 63 land thereby, in the manner previously described,

to cause the timer G8 to receive another impulse, which results in another cycle of operation cf the press. n

`It is to be understood that the above-described arrangements are simply illustrative of the application of the principles of the invention. Numerous other arrangements may be readily devised by those skilled in the art which will embody the principles of the invention and fall within the spirit and scope thereof.

What is claimed is:

A device for controlling the current to a load comprising a source of current, a timer connected to said source and operable upon the completion oi an auxiliary circuit thereto to close a contact pair of the timer and maintain them closed for a predetermined interval, said contact pair having one contact connected to one side of said source, a relay having one side of its winding connected to the other side of said source and having the other side of its winding connected to the other` Contact of said contact pair, a latch actuating electromagnet having one side of its winding connected to said one side of said source and the other side of its Winding normally connected through a pair of manually operated switches connected in series to the other side of said source, and a second relay having its armature positioned to be latched by the latch actuating eleotrornagnet when said electromagnet is deenergized, said second relay having one side of its winding connected to said one side of said source and having the other side of its'wind ing connectible in series to said switches in their off-normal or operative positions to the other Side of said source, saicl auxiliary circuit being under control of said second relay for closing said contact pair to initiate the operation of the timer whereby actuation of both of said switches is necessary to render the latch-actuating electromagnet potentially effective and return of both of said switches is necessary before another cycle of operation can be initiated.

NAT A. L. GULL. BROR V. MALMBERG.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS 

